Conventionally, various schemes are known and adopted as coding schemes for encoding binary images in image storage apparatus for encoding, storing, and managing digital images. For example, facsimile machines adopt Modified Huffman (MH), Modified Read (MR), and Modified Modified Read (MMR) coding schemes, by which images to be transmitted or received are encoded, then stored and managed in memory, and used for communication.
In the example of facsimile transmission, originals are scanned page-by-page and converted into digital signals so as to be stored as codes. At this time, information such as the page number, the horizontal scanning width, the number of lines, the resolutions, and the coding scheme is stored as page management information for each page. Further, when the encoded data is transmitted, the receiver machine is informed of necessary information based on this management information.
Recently, however, the JBIG (Joint Bi-level Image Group) coding scheme described in ITU-T recommendations T. 82 and T.85 came to be adopted for further enhancement of communication rates and encoding efficiency. In the JBIG coding scheme, encoded data (BIE) on a given page consists of a header (BIH) portion that stores parameters therein and a data (BID) portion that is image data. The header (BIH) portion includes parameters specifying the image size, the encoding mode, etc., for encoding/decoding, and it consists of 20 bytes of data.
However, this conventional manner of storage and management with the JBIG coding scheme has a problem that information for each page is stored in both the page management information and the header (BIH) portion with the result of inefficient use of memory.
For example, when originals to be transmitted are scanned page-by-page, the number of scanning lines on each scanned image is stored in the page management information. Then, because digital signals of the scanned images are JBIG-encoded, the number of encoding lines on each page is also stored in the header (BIH) portion of the JBIG-encoded data (BIE), and the number of the encoding lines and the number of the scanning lines are the same parameter. Thus, storing the same parameter in the page management information and the header (BIH) portion cannot be considered as efficient use of memory.